Modern reflective displays, such as typical electrophoretic displays, are fabricated in a sandwich structure that includes an electronic backplane, a display media and a counter electrode. The electronic backplane and the counter electrode together generate an electric field that controls the reflectivity of the sandwiched display media. Individually controlling the electric field applied to pixels enables image formation. Observers view the image through the counter electrode
A flexible reflective display is highly desirable because of its paper-like qualities. Owing to the presence of the display media, both the backplane and the counter electrode are subject to significant mechanical stress when such a display is bent. A first problem with such sandwich structures is that it is difficult to make transparent highly flexible counter electrodes. Current transparent flexible counter electrodes are fabricated by depositing indium tin oxide on Mylar to form a counter electrode. However such counter electrodes suffer from lack of high flexibility or stretch-ability. Ideally, an elastomeric transparent conducting counter electrode is highly desirable.
However, transparent conductive elastomeric materials are not currently available. Elastomeric conductive materials can be made by adding conductive materials such as graphite, gold particles, nickel plated particles and the like to an elastomer. However, the resulting material is not transparent and thus inappropriate for a counter electrode.
In color displays, each pixel output is typically a function of the pixel state of display material and a color filter corresponding to each pixel. The color filter determines the color of the light reflected. Each color filter is typically patterned directly on the counter electrode. However patterning color filters on a flexible counterelectrode presents alignment problems both during and after manufacture.
Attaching the color filters to the counter electrode means that during assembly, the counter electrode must be precisely aligned with the electronics in the backplane. During operation, the filters should remain aligned with the control electronics in the backplane so that each pixel outputs the desired colored light. This alignment maintenance can be difficult when the display flexes.
Thus, an improved display system is needed.